Earth Bondhon
Creators
Rojony Khatun Author
Rojony Khatun
CalculatorToolsProjectExpert
Reviewers
Małgorzata Koperska, MD Steven Wooding
Last updated: September 21, 2025

Delay LED Light Circuit Using BC547 Transistor

🇺🇸
English
Default
🇪🇸
Español
Spanish
🇫🇷
Français
French
🇩🇪
Deutsch
German
BC547 Transistor

BC547 Transistor

General-purpose NPN bipolar junction transistor (BJT)

3V LED 5mm

3V LED 5mm

3V, 5mm round light-emitting diode

Push Button Switch

Push Button Switch

A simple mechanical switch used to make or break a circuit when pressed. It returns to its original position once released. Commonly used in doorbells, calculators, reset buttons, and control panels.

[push-button-switch]
4.7k Fixed Resistor 1/4W

4.7k Fixed Resistor 1/4W

A 4700-ohm resistor rated for 1/4 watts

10K Fixed Resistor 1/4W

10K Fixed Resistor 1/4W

A 10,000-ohm resistor rated for 0.25 watts

[10k-fixed-resistor-1/4w]
1000µF Capacitor

1000µF Capacitor

Large electrolytic capacitor with 1000 microfarads

*Please note: These are affiliate links. I may make a commission if you buy the components through these links. I would appreciate your support in this way!

Delay LED Light Circuit

Control the LED light with an adjustable delay using a BC547 transistor. Simple RC-based timing circuit for smooth LED ON/OFF transitions in DIY projects.

adjustable LED on-off delay

BM547 is a Delay LED light circuit that offers smooth LED turn-on/off timing. The transistor switches slowly using an RC network, with the delay being adjustable to lighting applications.

DIY LED delay controller

The Delay LED Light Circuit with BC547 enables the controlled turn on/off of an LED with a delay, which lets the transitions be smooth. An example of an NPN transistor used extensively is BC547, which is a switch driven by an RC (Resistor-Capacitor) timing network. As the input is converted, the capacitor charges or discharges through the resistor, which progressively switches the transistor on or off. The LED is lit up based on the conduction of the transistor, giving a variable delay based on the values of the RC. It is ideal for lighting staircases, indicator lamps, hobby electronics, and ornament lighting. The delay time may be adjusted by adjusting the resistor or capacitor. It is a simple design that is cheap and simple to assemble on a PCB or a breadboard. It is also appropriate for novices who need to know about timing circuits and switching with a transistor.

Work / Installation (Inputs → Outputs)

  • Power Input → DC supply (e.g., 5–12V).
  • RC Network → Resistor and capacitor create charging/discharging delay.
  • BC547 Transistor → Acts as a switch to control LED.
  • Output → LED turns on/off gradually according to RC timing.
  • Installation → Assemble on PCB or breadboard; connect LED and resistor properly; adjust RC values to set desired delay.

Testing & Final Adjustments

Once assembled, connect the power supply and note the operation of the LEDs. The delay can be varied by changing the values of resistors or capacitors. Make sure that the LED does not flicker. Check to ensure that the BC547 transistor is not overheating when using it. Test at different levels of voltages to ascertain a stable performance. Adjust RC values to best delay effect. This is because proper testing will provide a quality and efficient delay LED light that can be used as a staircase lighting, ornamentation, and hobby electronics project.

Frequently Asked Questions - Delay LED Light Circuit:

What is BC547 used for?

It is an NPN transistor used to switch the LED in this circuit.

Can I adjust the delay?

Yes, by changing the resistor or capacitor values in the RC network.

Is it beginner-friendly?

Yes, simple circuit suitable for learning timing and transistor switching.

What voltage is required?

Typically 5–12V DC, depending on the LED and resistor.

Can it drive multiple LEDs?

Yes, within the current rating of BC547 and resistors.

Do I need a heatsink?

No, BC547 handles small currents without a heatsink.

Is it suitable for decorative lighting?

Yes, commonly used in DIY and decorative LED projects.

Can it work with RGB LEDs?

Yes, separate RC circuits can be used for each color channel.

Can I use a different transistor?

Yes, any small NPN transistor with similar ratings can work.

Is it cost-effective?

Yes, uses readily available components like BC547, resistor, capacitor, and LED.

Rojony Khatun

Rojony Khatun

CalculatorToolsProject

Rojony Khatun is the creator of a free online tools website designed to simplify everyday and engineering-related calculations for students, professionals, and hobbyists. The platform offers a wide variety of basic and advanced calculators across key categories, including Electrical Calculators, Electronic Calculators, and Time & Date Calculators, helping users solve problems quickly and accurately.